Japan's two biggest airlines said on Monday they had begun replacing the powerpacks on their troubled Dreamliner aircraft after US aviation authorities' approved Boeing's battery fix proposal.

All Nippon Airways, the next-generation aircraft's biggest operator, started installing the new battery system into five of its 17 Dreamliner planes at a handful of Japanese airports, a company spokesman said.

The replacement could take as long as two months, with the carrier eyeing a resumption of flights in June, he added.

Japan Airlines also began replacement procedures for two of its seven Dreamliners at Haneda and Narita airports in Tokyo on Monday.

"We began the work as we have received instructions from Boeing following the FAA's approval," a company spokesman said.

"But we have not decided on the timing of 787 flight resumption," with final approval to come from Japanese regulators, he added.

On Friday, the US Federal Aviation Administration approved Boeing's proposed battery fix for its 787 Dreamliner aircraft, a key step toward getting the grounded jetliner back in the skies.

Airlines will receive instructions on how to implement the fix of the problematic lithium-ion batteries that overheated, prompting the worldwide grounding of the 787 in mid-January, the FAA said.

Last week, a Japanese newspaper reported that Tokyo planned to impose additional safety requirements on its airlines before they are allowed to resume flying the Dreamliner.

The grounding of the 50 Dreamliners in service came after a battery fire on a parked JAL 787 at Boston's Logan International Airport and an incident in which fumes from a battery forced the emergency landing of an ANA-operated plane in Japan.